The overall goal of this program project grant is to elucidate the molecular organization of intracellular signaling pathways involved in mediating the specificity of neural and neuroendocrine responses. The unifying theme is that this organization process depends upon cytoplasmic and nuclear scaffolding proteins that have the ability to integrate diverse signaling cascades. The first goal, addressed primarily by Drs. Goodman and Soderling, is to determine how two widely utilized transcriptional coregulators, CBP and CtBP, contribute to the regulation of genes involved in cell differentiation, development, and apoptosis. While much is known about the interactions of individual transcriptional activators and repressors with specific co-activators or co-repressor , little is known about how these co-regulators are regulated. Experiments in this proposal are designed to increase the understanding of this regulation. The second goal, addressed principally by Drs. Scott, Soderling, and Goodman, is to determine how protein kinase A (PKA) and calcium/calmodulin (CaM)-dependent protein kinases promote changes in cell shape in movement. These studies, which focus on the role of actin polymerization in cellular dynamics, are an extension of the A- kinase anchoring protein (AKAP) hypothesis, a widely accepted model developed in the Scott lab that explains key elements of intracellular signal integration. The regulation of actin polymerization is also addressed in the third goal to characterize the functions of noel mediators of endocytosis and exocytosis. This goal, addressed primarily by Drs. Almers and Scott, utilizes a new technique developed by Dr. Almers, evanescent field microscopy, to visualize components of the endocytotic machinery adjacent to the plasma membrane. Drs. Almers and Goodman will also utilize this approach to elucidate the function of a protein domain that appears to be involved in both transcription and exocytosis. Collaborative experiments involving multiple principle investigators constitute the foundation of the program. Core laboratories for cell culture, protein chemistry, and administration are designed to allow the proposed studies to be performed in an efficient and cost-effective manner.